Article peer reviewing is regarded as an important element for ensuring quality in research.
To find out if a journal is peer reviewed use Ulrich's Periodicals Directory. Look up the title of the journal and see if it has the Refereed symbol next to it (more detail is on the site).
The Open Access movement has resulted in an exponential increase in the number of new online publishers. Many of these publishers are very questionable (please be aware) and might exist only to make money off the author processing charges that are billed to authors upon acceptance of their scientific manuscripts. Consult the following resources to identity practices used by predatory publishers as well as lists of open access journals that re considered non-deceptive.